There’s no sound quite like the clatter of pool balls coming together on a break shot. It’s a satisfying sound that makes people curious about the insides of pool balls. It also begs questions about what makes that specific sound. You may have noticed that not all pool balls sound exactly the same. So, let’s get to the center of things by answering the question: Are pool balls hollow?
Pool balls are not hollow. They are solid all the way through because they need to be similar in weight, density, and physical properties. In theory, you could make hollow pool balls that were the same weight and density, but it would complicate the manufacturing process significantly.
Why Are Pool Balls Solid?
There are certain characteristics that good pool balls need to share.
- Smooth Surface
The weight and size of the pool balls come together to determine why pool balls are solid and not hollow. The weight is the most important part of the equation. If pool balls were hollow, they would be lighter overall. While this wouldn’t matter too much if all the other balls were the same weight, it would likely be harder to keep the balls on the table during play.
Pool balls weigh as much as they do because it makes for consistent play and feel. Standard American pool balls weigh between 5.5 oz. and 6 oz. And, in order to maintain the weight of a hollow pool ball, they would likely have to be larger. The various sizes of billiard balls are as such to make the game challenging, to maintain consistency, and to match the pockets, tables, and cues.
Imagine playing pool with balls the size of softballs!
Drawbacks of Hollow Balls
Aside from the obvious issue of manufacturing hollow pool balls, there are some drawbacks that hollow balls would present.
If today’s pool balls were hollow, they wouldn’t be as durable. The solid spheres that are today’s pool balls can hold up better to repeated collisions than if they were hollow.
Without getting into the math of a hollow and solid sphere, let’s just say that the physics of the game as we know it would change. Hollow spheres behave differently than solid spheres, which would affect nearly every aspect of gameplay. Essentially, if we had pool balls that were hollow, pool would be a different game, requiring different tactics to win.
We’ve mentioned this above, but it bears repeating. Creating a hollow sphere that is solid enough to maintain its shape and avoid breaking after thousands of collisions would be expensive. Sets of pool balls would likely be triple what they cost today, just for this reason.
Now that we’ve discussed why pool balls aren’t hollow, let’s look at what’s inside them.
What’s Inside a Pool Ball?
If pool balls aren’t hollow, then what’s inside of them?
Modern pool balls are the same on the inside as they are on the outside. That material is a hard and durable type of plastic. But the specific type of plastic depends on the ball manufacturer. Today’s balls are either polyester or phenolic resin. Take a look at this quick video to see the inside of a pool ball.
But not all pool balls are created equal. Phenolic resin balls are considered the “gold standard” of billiard balls today. And only one company makes them. More on that below, as we discuss a bit about the history of pool balls.
What Are Pool Balls Made Of?
As mentioned above, modern pool balls are made of phenolic resin or polyester. But it wasn’t always so. In fact, the very first pool balls were made of solid wood. This was a cheap and readily available option, but wooden billiard balls didn’t last very long and there was little consistency among them.
Enter Ivory Balls
Right around the 17th-century ivory started being used for many different things. Upper-class Europeans wanted ivory for canes, piano keys, and even billiard balls. But there were some issues with ivory, as well. Before too long it became clear that ivory harvesting was drastically reducing the elephant population. Plus, it was expensive.
Ivory balls were better than wood, but they still were a little lacking. They yellowed fairly quickly and had a tendency to crack over time or when struck with enough force. So, a billiard table manufacturer by the name of Phelan and Collender put out a $10,000 prize for anyone who could offer a better material for pool balls.
Related Article: How to Tell if a Cue Ball is Ivory
Plastic Billiard Balls Are Born
In an effort to win the big money prize, an inventor named John Wesley Hyatt got to work. He is credited for inventing one of the first plastics on his quest for a new billiard ball. This became known as Celluloid, and he used alcohol, camphor, and nitrocellulose to invent it.
But, Hyatt didn’t snag the $10,000 prize. His billiard balls weren’t as durable as ivory and they could explode during the manufacturing process.
It was another inventor who won the prize; a chemist by the name of Phelan Leo Baekeland invented a new substance which he called Bakelite. Bakelite was easily manufactured, durable, and non-explosive. So, by the 1920s, the majority of pool balls were made from this new synthetic material.
But, the age of plastics had begun, and pool balls changed again during the 20th century. A Belgian company called Saluc, founded in 1923, started manufacturing pool balls in the 1950s.
Today that company is still going strong and selling billiard balls under the name Aramith. They use phenolic resin to create balls that are durable, long-lasting, and precise. These balls are considered the best on the market, as evidenced by the 80% of market share they enjoy. They’re the only manufacturer that uses pure phenolic resin in their pool balls.
The Aramith Process
Aramith balls are solid phenolic resin all the way through. They’re chip and scratch-resistant. And the whole process of making billiard balls lasts 23 days.
They use precision computers and polishers to create quality balls. And, since the balls must be very close in weight, each ball is hand-picked for the set it will go in.
Phenolic resin is thermosetting, which means that it melts once when heated, and after it cools it can never be melted again. After the balls are created in a mold, they are then sanded and polished.
When looking at a stripe ball, you may think that the color is painted or layered on the outside. But this is not so with Aramith pool balls. As the video above shows, the colors are solid all the way through.
Other balls, like those made out of polyester, are often precision-painted after the balls are molded.
If you’re in the market for a set of quality billiard balls, I recommend this premium Aramith set available on Amazon.
There are several reasons why pool balls aren’t hollow, including the expense of making such balls and the changes in the physics of the game that would entail. Throughout the whole of billiard history, no balls have been intentionally hollow. From wood to ivory, Bakelite to phenolic resin, pool balls have remained solid all the way through.